Variable tread width vehicles are known in the art. U.S. Pat. No. 2,901,050 teaches a vehicle with laterally extensible wheel assemblies. The wheel assemblies of such vehicles are provided with sleeves that ride back and forth along shafts. The wheel assemblies may be extended or retracted by various mechanisms, such as bell cranks or hydraulic cylinders.
It is especially desirable to use variable width tread vehicles in agriculture to allow the vehicles to navigate through agricultural fields with varying wheel spacing and widths. One drawback associated with such prior art vehicles is the inability to securely lock the wheel assemblies against undesired lateral movement once the wheel assemblies are extended or retracted to their desired position. Bell crank linkages and hydraulic cylinders, such as those described in U.S. Pat. No. 2,901,050, have an inherent amount of play that allows the wheel assemblies to move back and forth laterally as the vehicle is in use. It would therefore be desirable to provide a variable width vehicle with laterally extensible wheel assemblies secured against excessive lateral play during operation.
Prior art agricultural machines sometimes have leg weldments secured to a metal shaft. The shaft is provided in a sleeve and coupled to a hydraulic actuator. To keep the hydraulic actuator from getting damaged as forces act upon the wheels, and to reduce play in the shaft/hydraulic actuator connection, the shaft is pinched against the sleeve with bolts. The bolts are preferably tight enough to buffer impact between the wheel and the hydraulic actuator, but not so tight as to prevent the hydraulic actuator from extending and retracting the shaft relative to the sleeve. One drawback associated with such systems is that they still allow undesirable play between the shaft and sleeve. Another drawback associated with such systems is the requirement of a large enough linear actuator to overcome the pinching force of the bolts. Yet another drawback with such systems is that as wear occurs on the bearing plates, the bolts must be periodically manually tightened to prevent undesired movement of the shaft within the sleeve. It would be desirable to provide a system that reduced undesirable play between the shaft and sleeve, and eliminated the need for repeated manual tightening of bolts, while allowing the use of a smaller linear actuator.
Another drawback associated with such prior art devices is the inability to steer the wheel assemblies. While it is known to drive such wheel assemblies, U.S. Pat. No. 2,901,050 does not teach any way to steer the wheel assemblies. It would therefore be desirable to provide a variable width vehicle with laterally extensible and steerable wheel assemblies.
Yet another drawback associated with such prior art devices is the inability to use such systems in high speed vehicle applications. While the use of small universal joints and worm gears may be satisfactory for driving crane carriers at low speeds, they are not sufficient to reliably drive vehicles at high speeds for long periods of time. It would therefore be desirable to provide a variable width vehicle with laterally extensible and capable of continuous high speed travel.
The difficulties discussed hereinabove are sought to be eliminated by the present invention.